Log message:
Add COMPILER lines to c++ ports which currently use the default. Adjust
some existing COMPILER lines with arch restrictions etc. In the usual
case this is now using "COMPILER = base-clang ports-gcc base-gcc" on
ports with c++ libraries in WANTLIB.
This is basically intended to be a noop on architectures using clang
as the system compiler, but help with other architectures where we
currently have many ports knocked out due to building with an unsuitable
compiler -
- some ports require c++11/newer so the GCC version in base that is used
on these archirtectures is too old.
- some ports have conflicts where an executable is built with one compiler
(e.g. gcc from base) but a library dependency is built with a different
one (e.g. gcc from ports), resulted in mixing incompatible libraries in the
same address space.
devel/gmp is intentionally skipped as it's on the path to building gcc -
the c++ library there is unused in ports (and not built by default upstream)
so intending to disable building gmpcxx in a future commit.

Log message:
Define variables with C linkage to match earlier declarations.
This fixes clang6 errors that "declaration in global scope conflicts
with declaration with C language linkage". None of these show up
on x86, but some do on aarch64 due to different #ifdef paths.
ok pirofti@

Log message:
Define variables with C linkage to match earlier declarations.
This fixes clang6 errors that "declaration in global scope conflicts
with declaration with C language linkage". None of these show up
on x86, but some do on aarch64 due to different #ifdef paths.
ok pirofti@

Log message:
Define variables with C linkage to match earlier declarations.
This fixes clang6 errors that "declaration in global scope conflicts
with declaration with C language linkage". None of these show up
on x86, but some do on aarch64 due to different #ifdef paths.
ok pirofti@

Log message:
Define variables with C linkage to match earlier declarations.
This fixes clang6 errors that "declaration in global scope conflicts
with declaration with C language linkage". None of these show up
on x86, but some do on aarch64 due to different #ifdef paths.
ok pirofti@